The disclosure of the following priority application is herein incorporated by reference: Japanese Patent Application No. 11-351435 filed Dec. 10, 1999.
1. Field of the Invention
The present invention relates to a lens holding frame that holds a lens used in a camera, a video camera or the like.
2. Description of the Related Art
A lens is secured to a lens holding frame in the prior art through caulking or with a retaining ring which is provided as a separate part. Alternatively, the lens is secured with an adhesive in recent years to achieve miniaturization and reduced weight, a cost reduction and the like.
Japanese Laid-Open Patent Publication No. 4-166904 (U.S. Pat. No. 5,493,452) discloses a lens barrel in the prior art in which an adhesive is used. Specifically, Japanese Laid-Open Patent Publication No. 4-166904 (U.S. Pat. No. 5,493,452) discloses an example in which an adhesive is allowed to penetrate through the capillary action in a lens holding barrel that does not require any lens eccentricity adjustment or lens inclination adjustment. A lens holding barrel such as that disclosed in this publication is suitable for use in conjunction with a lens provided at a position at which the eccentricity and the inclination of the lens used at the lens barrel do not greatly affect the overall lens performance of the photographic lens such as the resolving power.
However, the lens holding barrel disclosed in Japanese Laid-Open Patent Publication No. 4-166904 (U.S. Pat. No. 5,493,452) cannot be employed when the eccentricity and the inclination of the lens greatly affect the overall lens performance of the photographic lens such as the resolving power or when the lens eccentricity and the lens inclination are to be adjusted in the final adjustment of the entire photographic lens, and instead, a lens holding frame with an adjustment margin is used.
FIG. 11 shows a lens holding frame Ill and a lens barrel 110 in which a lens is bonded in a conventional manner by allowing for an adjustment margin. At the lens barrel 110, the lens holding frame 111 and a lens 112 are bonded with an adhesive 113 shown in FIG. 12.
The lens holding frame 111 holds the lens 112 and is provided to mount the lens 112 at a lens main body (not shown). The lens holding frame 111 includes a cylindrical portion 111a which cylindrically encloses and holds the external circumference of the lens 112 and three lens receptacle portions 111b constituting contact portions where it comes in contact with the lens to position the lens 112 along the direction of the optical axis and provided over equal intervals, and it may be prepared by injection-molding polycarbonate.
FIG. 12A presents a sectional view through Oxe2x80x94O in FIG. 11 and FIG. 12B presents a sectional view through Pxe2x80x94P in FIG. 11. At the lens barrel 110 in the prior art, after the photo-curing adhesive 113 such as a visible light and ultraviolet light setting adhesive is allowed to fill and penetrate the space between the lens holding frame 111 and the lens 112 through capillary action, the adhesive 113 is caused to set by irradiating setting light to bond and secure the lens 112 at the lens holding frame 111. Unless the adhesive 113 is allowed to completely fill and penetrate the lens receptacle portions 111b, the required bonding strength cannot be achieved for the lens holding frame 111 and the lens barrel 110 in the prior art structured as described above. Accordingly, the adhesive 113 is normally used in sufficient quantity to fill and penetrate the lens receptacle portions 111b. 
However, the lens holding frame 111 and the lens barrel 110 in the prior art pose a problem in that even a slight change in the quantity of the adhesive 113 that is applied, the application speed, the viscosity of the adhesive 113 or the like or a positional misalignment of the tip of the nozzle of the dispenser used for adhesive application may result in the adhesive 113 spreading out into the range of the effective diameter of the lens 112, thereby causing loss of precision with regard to the lens position, ghosting, poor external appearance and the like.
If, on the other hand, the quantity of the adhesive 113 that is applied is reduced, for instance, in order to prevent the adhesive 113 from spreading out, problems occur in that the adhesive does not fully penetrate the gap between the lens 112 and the lens holding frame 111 and in that the bonding strength is lowered.
These problems will occur even more readily in the lens holding barrel disclosed in Japanese Laid-open Patent Publication No. 4-166904 (U.S. Pat. No. 5,493,452) mentioned earlier. Namely, since the positional regulation of the external circumference of the lens is achieved with the lens holding frame in this type of lens holding barrel, the adhesive is not allowed to enter the contact portions. Thus, it is necessary to inject the adhesive into the extremely small gaps around the contact portions (a 0.25 mm gap, since the diameter is bigger by only 0.5 mm in the example disclosed in Japanese Laid-Open Patent Publication No. 4-166904 (U.S. Pat. No. 5,493,452)). Consequently, the adhesive can be prevented from spreading out only through rigorous control of the quantity of the adhesive to be injected and the injection speed, which makes for an extremely difficult work process and a complex and time-consuming dispenser adjustment.
In addition, it is necessary to use an extra fine dispenser nozzle corresponding to the size of the gap during this process, which tends to lead to clogging and deformation at the tip of the nozzle to result in poor operability.
Furthermore, since the lens is allowed to drop well into the cylindrical portion of the lens holding barrel in the example disclosed in Japanese Laid-Open Patent Publication No. 4-166904 (U.S. Pat. No. 5,493,452), the direction along which the nozzle can be inserted is restricted to compromise the operability and also the position of the nozzle of the automatic machine is restricted. Thus, it is difficult to adopt the disclosure of the publication in an actual process.
An object of the present invention is to provide a lens holding frame and a lens barrel in which the adhesive is not allowed to spread out into the range of the lens effective diameter to achieve good operability and stable and sufficient bonding strength.
In order to attain the above object, a lens holding frame according to the present invention that secures and holds a lens, comprises: a lens holding frame main body; a plurality of lens receptacle portions projecting inward at the lens holding frame main body and formed at the lens holding frame main body so as to position the lens along a direction of an optical axis of the lens by placing the lens in contact along the direction of the optical axis; and a plurality of injection portions formed inward at the lens holding main body through which an adhesive for bonding at least the lens and the lens receptacle portions is injected.
In this lens holding frame, it is preferred that the injection portions are each provided with a reservoir portion where some of the adhesive is collected.
Also, it is preferred that the injection portions each assume a structure with a wide intake side where the adhesive is injected and a narrow inner side. In this case, it is preferred that the injection portions each include an inclined surface having a wide intake side where the adhesive is injected and gradually narrowing further inward. Furthermore, it is preferred that the inclined surface includes a reservoir portion where some of the adhesive is collected.
Also, it is preferred that the injection portions are set at positions adjacent to the lens receptacle portions.
Also, it is preferred that the injection portions are provided on a side where the lens receptacle portions come into contact with the lens. In this case, it is preferred that the injection portions are formed so as to allow the adhesive which has been injected to penetrate gaps between the lens and the lens receptacle portions due to gravity and capillary action while any excess adhesive remains at the injection portions when the lens is set at the top of the lens receptacle portions by aligning the direction of the optical axis of the lens with a direction of gravity.
Also, it is preferred that the injection portions are provided on a side opposite from a side where the lens receptacle portions come into contact with the lens. In this case, it is preferred that the injection portions are formed so as to allow the adhesive which has been injected to penetrate gaps between the lens and the lens receptacle portions due to gravity and capillary action while any excess adhesive remains at the injection portions when the lens is set at bottoms of the lens receptacle portions by aligning the direction of the optical axis of the lens with a direction of gravity.
A lens holding frame according to the present invention that secures and holds at least two lenses that are a first lens and a second lens, comprises: a lens holding main body; a plurality of lens receptacle portions projecting inward at the lens holding frame main body, positioned between the two lenses and formed at the lens holding frame main body so as to position the two lenses along a direction of an optical axis of the two lenses by allowing the two lenses to come in contact along the direction of the optical axis; a plurality of first injection portions formed inward at the lens holding frame main body, through which an adhesive for bonding at least the first lens and surfaces of the lens receptacle portions located toward the first lens is injected; and a plurality of second injection portions formed inward at the lens holding frame main body further toward the second lens and further outward relative to the first injection portions, through which an adhesive for bonding at least the second lens and surfaces of the lens receptacle portions toward the second lens is injected.
A lens barrel according to the present invention comprises: a lens; and a lens holding frame that secures and holds the lens. And the lens holding frame comprises: a lens holding frame main body; a plurality of lens receptacle portions projecting inward at the lens holding frame main body and formed at the lens holding frame main body so as to position the lens along a direction of an optical axis of the lens by placing the lens in contact along the direction of the optical axis; and a plurality of injection portions formed inward at the lens holding main body through which an adhesive for bonding at least the lens and the lens receptacle portions is injected.
In this lens barrel, it is preferred that a portion of the adhesive is collected at the injection portions.